The invention relates generally to the field of printing, and in particular to electrographic printing methods and apparatus.
An electrographic printing process wherein a magnetically responsive electrically conductive toner material is deposited directly on a dielectric receiver as a result of electronic current flow from an array of magnetically permeable styli into toner chains formed at the tips of the styli as disclosed in an article entitled xe2x80x9cMagnetic Stylus Recordingxe2x80x9d by A. R. Kotz, Journal of Applied Photographic Engineering 7:44-49 (1981).
The toner material described by Kotz is a single-component, magnetically responsive, electrically conductive toner powder, as distinguished from multiple-component carrier/toner mixtures also used in electrophotographic development systems. The magnetically permeable styli described by Kotz are a linear array of magnetically permeable wires potted in a suitable material and arranged such that the ends of the wires are perpendicular to the receiver surface. A major advantage of this system is that it operates in response to relatively low voltage control signals (of the order of 10 volts), thereby allowing direct operation from inexpensive integrated circuits.
One shortcoming of the printing process described by Kotz is that the resolution of the printing system is limited by cross talk between the styli in the print head. Another shortcoming is that the single-component magnetically conductive toners have a limited color gamut (black and brown) and therefore are not suitable for making color images. It would be desirable to make a full color printer using an electrographic printing technique.
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention a print head for an electrographic printer of the type having a magnetic brush for transporting magnetic developer to a recording region and a receiver for receiving an imagewise pattern of a component of the developer at the recording region, includes: a substrate defining a plurality of parallel microchannels for confining the developer to flow in the microchannels; and a corresponding plurality of selectively addressable transfer electrodes located at the bottom of each microchannel for selectively transferring the component of the developer to the receiver from the microchannel.
These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.
The microchannel print head of the present invention is advantageous in that it is capable of producing a high quality color image due to the excellent isolation between channels. The print head can be fabricated using a variety of well known techniques including stamping, micromachining, and photofabrication using a variety of materials.